Directional coupler



Aug. 12, 1952 A H. A. WHEELER DIRECTIONAL COUPLER 5 Sheets-Sheet 1 Filed May 16, 1946 INVENTOR.

D A. WHEELER,

TORNEY BY r 47 12, 1952 H. A. WHEELER 2,606,974

DIRECTIONAL COUPLER Filed May 16, 1946 5 Sheets-Sheet 2 Length 0? Side Line FEGI? INVENTORI HAROLD A. WH ELER,

ATTORNEY.

1952 H. A. WHEELER 2,606,974

DIRECTIONAL COUPLER Filed May 16, 1946 3 Sheets-Sheet 3 FIG. 8a 89 JNVENTOR. 0 A. WHEELER,

ATTQRNEY.

Patented Aug. 12, 1952 Harold A. Wheeler, GreatNeckyiNiig-assignor to Hazeltine Research, Ina,

rationv of Illinois Chicago, 111., a corpo Application May is, 1946; se'rni No. 670,081

11 Claims. 1 The present invention relates to systems for translating wave signals of various wave lengths and, particularly, to such systems utilizingwave guides such as transmission lines by which to select between Wave signals traveling in opposite directions in the same path of propagation.

Wave guides are widely used. to guide the propagation of wave-signal energy along a restricted path between two spaced points such, for example, as between a Wave-signal transmitter and its associated wave-signal antenna system or between a receiving antenna system and a wavesignal receiver. The term Wave guide as used in the present specification and claims applies to a system of longitudinal conductive surfaces which act as, the lateral boundary of an electricwave and have the ability of directing the propagation of such Waves, much as the rigid wall of a speaking tube is used to guide sound by preventing the sound from spreading into space. Wave guides may take the form of a pair of conductors in open space, such asa power line or a telephone line, or may comprise one conductor enclosed within but electrically insulated from a second conductor as in a conventional coaxial transmission line, or may simply comprise a single hollow conductor having such transverse dimensions as to render it capable of propagating an electric wave through the interior of the conductor.

It is usually desirable when using wave guides that the wave-signal energy shall flow along the wave guide only inone direction during-a given operating condition of the wave-signal system since this gives rise to maximum eificiency and stability of the system operation. Any wavesignalenergy flowing along the wave guide simultaneously in both forward and backward directions results in standing waves of potential and current along the wave guide. The presence of such standing waves thus is often indicative of impaired system efliciency and is conducive to undesirable instability of the system operation.

In certain applications of wave guides, however, standing waves are deliberately created along the wave guide to attain a particular result. Typical of such applications is the radio-frequency impedance-measuring systemwherein an impedance of unknown value is coupled to the end of a wave guide of known characteristic impedance and the maximum and minimum values of any standing waves created along the wave guide are observed as a measure of the magnitude and phase angle of the unknown. impedance.

In all such applications of wave guides, it consequently is frequently desirable to provide an arrangement for indicating the presence of standing waves as an indicationof an undesirable operating condition or formeasuring the values of a standing wave as a measure of the unknown value of an impedance which gives rise to the standing wave. "Additionally, it often is desirable that the actual value of wave-signal power supplied from a wave-signal source to a load deviceibe easily and readily measured without regard to the presence or. absence ofstandmg waves along a wave guide which couples the source to the load device.

Measurements'of the maximum and. minimum amplitude values of a standing wave, commonlyreferred to as a measurement of the "standingwave ratio, and measurement of the power supplied to a load device have heretofore-been accomplished by a so-called slotted waveguide. The slotted waveguide is a section of waveguide preferably 1 longer than one-half wave length and having a longitudinal slot in the outer conductor thereof by which a capacitive-pickup probe or an inductive-pickup loop may be inserted into, the electromagnetic field within the wave guidewThis probe or 1009 is movable within in construction or as convenient in operation as is desirable and is characterized byseveral wellvknown limitations and disadvantages.-

In certain applications where wave guides are used for wave-signal propagation, it is desirable that the value of wave-signal energy flowing in one direction along the wave guide be selectively measured without the measurement being affected by any wave-signal energy flowing in the opposite direction. One prior arrangement for efiecting-such measurement includes a loop of wire inserted into the electromagnetic field of a Wave guide of the coaxial transmission-line type to provide both magnetic and electric coupling with the inner conductor of the line. This .loop within the transmission line is connected between a resistor and indicating circuit. By proper selection of the values of magnetic and electric couplings between the loop and the inner conductor of the line, and the value of the terminating resistor, the magnetic and electric couplings add together in the indicating circuit for a traveling wave of wave-signal energy propagating in one direction along the transmission line but cancel out for a traveling wave in the reverse direction. This arrangement has the important disadvantages that the magnitude of wave-signal energy coupled into the pickup loop decreases rapidly with increasing wave length, so

that the arrangement is highly frequency selective. This is caused by the loop being much shorter than one-quarter wavelength so .that

the coupling is small at best/the" coefficients of magnetic and electric couplings between the pickup loop and the adjacent-length of transmission line being substantially less than unity.

There is the additional disadvantage thatproper operation of the arrangement necessitates a criticalgorientation'of the pickup loop relative to the .axisof the transmissionline by :which ,to select the correct value of mutual inductive coupling. Inrgeneral, the circuit configuration-required to attainrthe, desired operation israther criticaland cannot .be computed in advancebut can be :establishedronly-by a careful adjustment through the processoftrialand error.

113 1553111 object of the present invention, therefore, to provide a new and improved system for translating wave signals and onewhich avoids one or more of the disadvantages and limita- .tionsof' prior such systems of the type described.

It is a further object of .theinventionbtoprovide' a. system for translating wave signals, which permits: a transfer ofxwave-signal energyfrom azwave-signal propagation path in free space to a wave. guide, or from the propagation path of one wave. guide to another wave guide, with the direction and directional magnitude of' transferred wave-signal energy'flow in the wave guide selectively dependent upon an individual direction and directional magnitude of energy flowin the propagation path.

It is an additional object of-the invention to provide a wave-signal translating system, which easily and readily enables accurate measurements-to be made of the individual" wave-signal energies flowing in each of two directions along a wave-signal propagation path;

It'is yet another objector the invention to provides. novel system for translating wave signals, which permits a selectableportion of wavesignal energy traveling along a wave-signal propagation path to be abstracted therefrom selectively inaccordance with the direction ofenergy flow along the path.

T It-is a further objectof the invention to provide a new and improved system fortranslating wave signals which provides substanti'allynoattenuation to wave signals having wave lengths within a given range of wave lengths but which 'provides'substantial attenuation to wave signals having "wave lengths within wave-length ranges located just above or just below the given range.

"Conversely, the system may be arranged to attenuate wave signals in a given range and to rated bya distance much less than their length and much less than the wave length of the translatedwave. signals. The firstand second-mentioned paths have distributed magnetic and electric coupling therebetween through said aperture. The translating. system includes means for terminating the wave guide at one end thereof by an impedance having such value that substantially no wave-signal energy is developed at the otherend of the wave guide in response to a pure traveling Wave traveling through the first-mentioned path in the region or" the parallel portions of the aforesaid paths and in a direction corresponding to the direction from the one endto the other'end of the wave guide.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the followingdescription taken .in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

Referring now to the drawings, Fig. .1 illustrates schematically a wave-signal translating system embodying the present invention in a particular form; Fig. 2 represents an equivalent arrangement of the Fig. 1 translating system; Fig.3 is a circuit diagram, partly schematic, of a measuring. system which utilizes a-wave-signal translating system of the present invention; Fig. Sarepresentsa portion of a measuring system of the-Fig. 3 type but of slightly modified form; Figs. 4,5,7, 8, 8a, 9, and 10 illustrate schematically several modified forms of the invention; and "Fig. 6 graphically represents a translating characteristic of the Figs. 5 and 7 modifications of the invention. 7

Referring now more particularly to Figfl of the drawings, there is illustrated schematically-a system for translating wave signals embodying the present invention in a particular form; This system includes a first wave guide, shown as of the coaxial transmission-line type having an outer'conductor l0 coaxially surrounding an inner conductor H, for translating wave signals of the system along a predetermined path and with a substantially planar wave front. The term wave front applies to a plane parallel to the mutually perpendicular lines of electrostatic and magnetic flux of the wave. in planar wave front is one which inherently has electric-field and magnetic-field patterns varying only in two dimensions, with the only variation in the third dimension being one of time, the energy of the wave signal being propagated in a certain direction without appreciable change of amplitude; that is, the wave-signal energy must not be spreading outward or focusing inward if the Wave signal is to have a planar wave front. The term coaxial is here used in its broad sense as meaning a line comprising an inner conductor substantially enclosed by a parallel outer conductor; that is, a shielded line having an inner conductor substantially enclosed by its return circuit. In this regard, it may be pointed out that the outer I to one Wall of the housing I3.

conductor need not in all cases fully enclose the inner conductor, but may have a cross section comprising three sides of a rectangle with the fourth side open since this form of outer conductor adequately shields the inner conductor in many applications. This transmissionline will hereinafter be referred to forconvenience as the main? transmission line to distinguish it from a .second wave guide,.hereinafter called the. side wave guide, which is included in the wave signal translating systemwave guide comprises .an inner conductor I2, spaced equidistant fromthe sides of a rectangular ity, it is preferable that the lengths ofv the main and side lines be much greater than their diameter and separation.

The translating system includes means for mov- 0 ing the second Wave guide in a direction normal to the axis of the first wave guide manually to adjust the coupling between the wave guides, which coupling is provided in a manner presently to be explained, to adjust the magnitude of wavef signal energy transfer between the first and second waveguides. This means comprises a movable diaphragm Id of conductive material and having apertures I5 and I6 through which the conductor I2 extends. The diaphragm I4 is supported at the end of a rod I'I, which maybe of conductive or insulating material, the rod in turn being slidably supported by a bushing I8 secured The diaphragm I-I is provided around its periphery with conductive spring fingers I9 which engage the interior walls of the housing I3. I

The main transmission line I9, I I and the side transmission line I2, I3 have magnetic and electric coupling therebetween only over limited approximately parallel portions thereof. This coupling is provided by a common, intercommunicating, longitudinal aperture or slot 29 between the main and side transmission lines. The length and width of the aperture 20'estab1ish the magnitude of the magnetic and electric coupling between the main and side lines. Insofar as the length of the aperture 20 is concerned, maximum coupling between the transmission lines is provided when the length of the aperture is equal to onequ.arter wave length, or an odd number of quarter Wave lengths, at a selected wave length of wave signals translated through the main line. This length of aperture not only provides maximum transfer of wave-signal energy from the main line to the side line, but additionally ensures that the magnitude of energy transfer remains very'nearly uniform over a rangeof Wave lengths of translated wave signals.

The translating system also includes means for terminating the side wave guide I2, I3 at aselected end thereof by a resistive impedance, comprising either of a pair of resistors 2| or 22 which is connected between an individual end of the conductor I2 and the diaphragm I4, this im- 6 pedance having such value that substantially no wave s'ignalenergy is developed at the other end of 'the sid wave guide -in response to a pure traveling wave traveling throu'gh the first wave guide 10, II at the region of the aperture 20 and ina direction corresponding to the direction from the other end of the side waveguide toward'the -selected end thereof. This'resistive termination of the side wave guide fully hereinafter. I 1 I,

The electric and magnetic coupling between the lines I0, H and -I2,' I3 over thelength ofthe slot-29 slightly modifies their-characteristic imwill considered more pedances at this region. The conductors "I I and I2 are thus provided with enlarged diameters,

normally onlyslightly enlarged :due to the small values of coupling butshown somewhat exaggerated in Fig"; 1' for purposes of clarity, to preserve uniform the values of characteristic impedance along the entire length of each line for a-selected spacin of the conductors II and I2 "and to minimize undue departures of the characteristic impedance from the desired value'for other spacings of the conductors II, I2.

While the "wave-signal translating'system of Fig. 1 is illustrated schematically, it'will'be understood that the inner conductor I I of the main wave guide is suitably supported in insulated spaced relation to the outer conductor I0 thereof and that the conductor I2 of the side wave guide is supported by suitable insulating means from, but in insulated relation to, the diaphragm I4.

.Considering now the operation of the wave-signal translating system just described, andreferring to Fig. 2 which represents an equivalent arrangement of the translating system, the characteristic impedance of the transmission line I0, I I is designated as R0 while that of the side line is designated B0. 'A source S of wave signals is shown coupled to one end of the transmission line III, II and this line is shown as terminated in conventional manner by a resistive impedance R0 having a value equal to the characteristic impedance of the line I0, II..

, It can be shown theoretically and. experimentally that the coeflicient 1% of mutual inductance, or magnetic coupling, between the lines II], II and I2, I3 is equal to the coefiicieni'fik; or capacitive coupling, or electric coupling, therebetween since the longitudinal dimensions of theyslot ever, have such phase relationships. that the currents induced in the transmission line I2, I3 by a pure traveling wave of wave-signal energy flowing in the line I0, II fromthe source S to the resistive impedance R0 add in phase at the resistor R21 but have opposing phase at theresistor R22. If the value of the resistor R21 is properly selected, in a manner presently to be explained, no reflection of wave-signal energy occurs at the resistor R21. Consequently,- a pure travelingwave traveling along the main transmission line Ill, I I in the direction from" the source S to the terminating impedance R0 causes wave-signal energy to be developedonly across rectionally'inaccordance with the direction of energy flow in the main transmission line Ill, I'I. Thus, any energy which travels along the main tranSmissionlineL-IEI, II in the direction from the terminating impedance R0 toward the signal and is constructed to satisfy Equation. 1.

acoacm generator s,'such as wave-signal energy caused if the resistor R22 also properly terminates the side line. As a consequence, the measured potentials or cur-rents at the resistors R21 and R22-PI'O" vide a measure of the wave-signal energies flowing in each direction along the main transmission linel0,- H. 'Byvirtue of this propertmthe device ris-zcalled-a i directive coupler.

The yalue of the resistorRn or the resistonRzz is; equalto thecharacteristicimpedance R9 of the sidetransmission-line. Aspreviously mentioned,

vthe electric and magnetic-coupling between the main and side transmission lines-modifies their characteristic impedance over the length ofthe aperturelll. It, is desirable that this portion of the side transmission :line; having the characteristic impedance R1, shall properly match the value of characteristic impedance-:Roof the remaining portion of-the side line to avoid reflections of wave-signal energy onthe side line at the endsof the aperture 20.. -This matching of .impedances iseffected by-so constructing the side .linethat the characteristic impedance R1 has a value given by the-relation:

where lc the value of either the inductive or capacitive 'coeli'icient of coupling between the transmission lines Hl, ll and l2, [3 for a selected valueof spacing oi-the conductors ll, 12.

The value of" the coupling coefi'icientlc is given by the; relation 2 where It may bementioned at this point that the side line causes no reflection of wave-signal energy on the main line when the side line is properly terminated by the resistors 2|, 22. as described Since Equation 1 involves the coupling. coeflicient k which in turn involves the spacing of conductors H and i2, absence of reflection at the slot 20 as last described, occurs only for the selected spacing of the conductors ll, I2 but is minimized for other values of spacing of these conductors.

It is also desirable that the characteristic impedance R3 of the main transmission line over the length of the aperture 20 be such that its modified value match the characteristic impedance R of the remaining portions of this line other desired level.

istic impedance R3 has a value given by the relation:

In a wave-signal translating system of theFig. 1, type, the'coefficient of coupling k is normally made quite small so that the value of the characteristic impedance R1 of the side line is approximately equal to its characteristic impedance R0. Similarly, and for the same reason, the characteristic impedance R3 of the main line is approximately equal to its characteristic impedance Rt. Where larger values of the coefiicient of coupling 1c are desired for a particular application, suitable values of the characteristic impedance R1 of "the side line and R3 of the main line as given by Equations 1 and 3 are established by proper selection of either or both the inner and outer conductor sizes of the side and main lines over the length of the aperture '20. This will'be explained more clearly in connection with a modified form of the invention presently to be described.

'TheFig. 1 wave-signal translating system is so constructed that the value of the coupling coe'fi'lcientis between the main and side transmission lines may be varied by adjusting the distance between the side line and the main line. Thus, axial movement of the rod [7 varies the spacing between the inner conductor 12 of the side transmission line and the inner conductor 1 I of the main transmission line. Increasing the spacing between the conductors decreases the coefficient of coupling k and thus decreases the magnitude of wave-signal energy coupled from the main line into the side line. This modification provides a form of piston attenuator. Since the side line moves always between the planar parallel sides of the housing iii, the coupling appears in the June 1935 issue of The Proceedings of the I. R. E., pages 5'78 et seq. If desired. a suitable calibration scale may lee-engraved on the rod l'lgiving the attenuation in decibels or units from a given reference output The magnitude of coupling between the main transmission line 10, H and the side transmission line [2, l3 varies, of course, with the width and length of the aperture 2%. Maximum coupling and uniformity of coupling over a wavelength range are provided, insofar as the length of the aperture is concerned, when the aperture has a length of approximately an odd number of quarter-wave lengths at a selected wave length of wave signals translated through the main wave guide. This length of aperture has the ad ditional advantage that even-order harmonically related wave signals are not coupled from the main transmission line to the side transmission line, or vice versa, a characteristic of substantial advantage in certain applications.

The energy translated to the output terminals of the main transmission line, for any given value of energy applied to the input terminals of the line, .is reduced by the value of energy coupled into the side transmission line. The ratio of the value of wave-signal energy at the output terminalssof the main line to that at its input terminals is a measure of the efficiency of wave- -signal translation along the main line. and also sequent transfer of maximum. wave-signal energy to the side transmission line, when the length of the aperture 20 is equal to an odd number of quarter-wave lengths. Maximum efiiciency of,

translation occurs when'the' length of the aperture 20 is an even number of quarter-wave lengths long. This characteristic of the translating systern is particularly advantageous in connection with certain modified forms of the invention, hereinafter to be described, which have such construction that relatively large values of the coefclcient of coupling is may easily be attained.

Fig.3 is a circuit diagram, partly schematic, of a measuring system which illustrates a particular application of a wave-signal translating system embodying the present invention. Elements of Fig. 3 corresponding to similar elements of Fig. l are designated by similar reference numerals and analogous elements by similar reference numerals primed. The main transmission line It), II is shown as utilized to couple a wave-signal generator 25 to a wave-signal utilization device 26. The generator 25 may, for example, comprise a wave-signal transmitter and the device 26 a wavesignal antenna. Each end of the side transmis-' sion line 12', i3 is provided with a pair of conductive rings 2? and 28, each supported by the inner'conductor of the line and movable therealong. Theserings are spaced from the outer conductor of the line and have an efiective. electricalleng'th sufficient to provide an impedancematching arrangement of the type disclosed and claimed in applicants copending application Serial No. 563,713, filed November 16, 1944, ene titled High-Frequency Impedance-Matching Device, no-w Patent 2,403,252, granted July 2, 1946.

A wave-signal rectifier 29 has an input circuit scale crossed-coil electrodynamometer 33. A;

wave-signal rectifier 3G similarly has an input .5 circuit coupled across a portion of the terminating load resistor 22 of the side transmission line and has an output circuit including in series an ammeter35, an adjustable resistor 36, and the other winding 3? of the electrodynamometer 33. The outer conductor ID of themain transmission line it, it is provided with a longitudinal slot at least one-half wave length long through which is inserted a probe 33 of a standing-wave indicator 33. This indicator is of conventional construction and includes a wave-signal rectifier for developing a unidirectional potential Varying with the wave-signal potential along the line I0, I I at the region of theprobe 38 and ineludes a'meter 38- for indicating the magnitude of the derived unidirectional potential.

Several initial adjustments are made on the measuring system described to adjust it for.-. proper operation and in order that the meters 3 EI,'

33 and 35 may be calibrated. The calibration of the meters 3B-and- 35 is in termsof'the wave-signal power fiowin'g in individual forward and backward directionsjalong the main transmis- The meter 33 is calibrated in-* terms of the ratio of maximum-to-minimum values of standing-wave potential or current de veloped along the main line) Infperiorming the sion line I0, I I.

first adjustment; the device 26 is so designed or adjusted that a'pure travelingwave'travels'along the main transmission line H), l lrromthege'n- V erator 25 to the device 2t. This condition-is indicated'by the standing-wave indicator 33 and 0ccurs when the latter indicates that the wave-signal potential along the main transmission line has substantially the same value at all points' When this operating condition has been estab-- lished, it will be recalled from the preceding description of the operation ofthe Fig. l arrange:

ment, that all of the wave-signal energy induced Y in the side transmission-line I2, I3 is developedacross the terminating resistor2l and no energy is developed across the terminating resistor 22 if reflection of wave-signal energy does not occur Consequently, the second adjustment of the system consists in matching the at the resistor 2|.

terminating resistor 2| to the characteristic impedance R0 of the'side line sothat no wave signal energy is developed across the terminating resistor 22 as indicated by the meters 33 and 35. The attainment of this condition may involve some adjustment-of the rings 2'I, in the; manner described in the aforementioned co pendin application.

energy only across the resistor 22. .The'resistor. 22 is now likewise matched by sliders 28;.s0'tha't;

no wave-signal energy is developed acrossthe re- 5 sistor 2I as-indicated by the meters 30 'anlli3ik.-

The side transmission line [2,13 is thenagain bodily'reversed with relation to the main transeiz mission line [0, II and a short circuitis placed.

on the main transmission line at the input circuit of the device 26. This short circuitacauses total reflection of the'wave-signal'energy,travel j; r ing from the generator 25 to thepointjof, short, circuit sothat equal wave-signal energies flow in both directions along themain transmission line.; The adjustable. resistors 3| and. 36 arenowad justed 'until theindicator of the meter 33 is..at.;: mid-sca1e,..the point marked infinity in Fig-M3.

The short. circuitxis now. removed from the main transmission line',I0 ,1I|..at the linput eir cuit of the device 26 again to establish agpure traveling wavegon'the main line. The meter 30 is now calibrated in terms of the, wave-signalv 5 power traveling to the. device 26,. the measurement of power at. the device 26 being made in;

conventional manner. This calibrationismade at the frequency of operation of the systemjcom y prising the generator '25 and the device26 or at relatively narrow? frequency range.

mission line is thereafter bodily reversed to :the

now properly .adjustedfor operation.

The operation of the measuring -.system-,=.de scribed is almost self-evident from the ;descrip tion of the system adjustment. The meter: 33.947;

original 5 condition and the ,.measuring-.system;.i.$;

ists-s a e: mdiats=.- iat 3 e ua eis saal 1..

t i sre flowing b t di ctio s. lon t e a n t n mi s on l 0, 1 a cond onTo ax m m. s a ing-ware 1. 31 9 on the. li

n Pos tion i d q tes-a ure t av n -.w v

e n .i t erate: t t ederiee 126- flection U1 m me- 5 it extre er i ti. handposition would indicate a pure traveling e fi wine al h m in e I. f." mt

ice t t e en at whi c no hapnenin p rt cu a angement o The w vena r we flowin a o th l ne] I 0, l l immt eeene aw z to thede e. 2. ismdicatedby-the meter while the wave-signal m em wine alon t 1 I0. I in r r eci qni in c te b -the m t i Fig 3 1 .aci c t a am o 'r t np a asurin s st m s r-t at. i .3 Simir,

l eelement l-b ne. d i nat d r m l r .r ferr ms-n me a s.e epthat the ec rod nem meter 33 of the ;Fig. 3 arrangement is replaced in theinstant arrangement by an ammeter 43 havc ,one. c r n w ndin t u put/circuit. of the rectifier 29 .anda second current winding included inthe output circuit. of the rectifier 34...:The magneticfields of the windings lland.

45 opposeone another, The meter 43 is a zero center.-scale, type of meter and readingsto one. side. of its center-scaleposition indicatethe netwave signal power flowing from the. generator 25 to the device. 26 while deflections of the meter on the opposite side of center scale would indicate a net-power flowing .from the device 26 to the generator.25.. In this case, ,it is required that recti;

fiers 29 and 34 be of the square-jaw .typabr bee thermaldevices, with .output current proportionalato power.

Fig.4 illustratesa modified formof thewavesignal translating .systemmf thepresent invention which is essentiallysimilarin operation to thatlof Fig.1 butwhichzinvolves a slightly different structure. .Theisystem of Fig. 4 includes, 1 a firstor maincoaxial. transmission line; 48,; 49 y Y and asecond coaxial transmissionline positioned.

in concentric relation outside of -.the.;.firs t line witli a conductoricommon'toboth;ofthe lines. This second'or side transmission line .comprises,

an outerconductor 50 and the. commonpon: ductor 49 and is closed at the ends. by conductive.

apertured discs 5!, 52 which support the con-.,.

ductor 50 in concentric relation :with the ...con-.-;.

ductors- 48 and 49.=The common. conductor .49

has a'n "aperture or slot 53 dimensioned, as ex--. plained in'connection withtheapertur'e orslot 20 oi thLFig. larrangement, to permita desired... amount of magnetic and electi icLcoupling. be.-,. tweenithemain transmission lineandthe side transmission line. connected to the side .transmissionnline 49, 50

A coaxial connector..54 ;is "60 at apointthereonspaced a quarter-wave. length distant from that end of'the side line which, is closed by thedisc 5| while a coaxial. connector. is alsoconnectedto :thesideline; at. a point:

spaced one'quarter-wave length distant; from its other closed end. The. connectors. 54 and 55 arev terminated. by respective resistive .impedew ances 5B and. 51 properly to terminate the; side line .as explainedabove with referenceto Fig; i. In th'e=.operation..of this modified formgof the invention, the portion. of thesidelinebetween;

the connector- 54 '.and .the1..adjacent ,shortcircuitedend 51. of the line, acts in conventional manner as a quarter-wave impedance 1transformer" short-cir'cuited. at. its, remote end thus p en rh s impedance tto .wave-si' nal-xm ergy'at the point of connection of-the'connector. 54.; This is characteristic alsoof that portion of 5;.- the side transmission line between the connector 55 and the adjacent short-circuited end 52 .Of 4 the sideline. The operation and characteristics of this modified form of the invention are otherwise essentially similar to those of Fig. 1 and will not be repeated.

'63 and spaced from both of the conductors 6.0 andv 63.

side line and thus be a conductor commonto Either of the conductors or .63 v as... desired may constitute the other conductor of the both lines, For reasons of convenience presently. to be mentioned, theside transmission linev is shown as comprising the conductors 63 and B2.

In the .present modification, the transmission lines have conductor sizes soselected over the.

lengths of the second line as to provide a com! bined impedance for the two lines substantially equal to the characteristics impedance of the first line 60, 6| and to establish between the,

lines a desired amount of 'magneticand elec-.

ductor 6| of the first and second lines with the section 63.0f enlarged diameter. If the c haracteristic impedance of the first transmission.

line 60, 6! beyond the second line 62, 63 has a value R0", the characteristic impedance of the first line'wili be constant. along its entire length,

, trio coupling. This is accomplished in the pres-.

ent arrangement by providing the common con- I if the sizeof the outer-conductor portion 63 is selected with relation to the diametersof the, conductors r66, 62 tosatisfy the followingrelation;.

Rz=thewcharacteristicimpedance of the line seesection between the conductors 60 and B2, and R1'=,thecharacteristic impedance of the line between the conductors 62, B3.

Resistive means, comprising one or more re sistors 64, 64, is coupled-between conductors 6 2,

63 of the side line at one end thereof for termi nating the side line by a resistive impedance having such value that substantially no wave-signal energy is developed at the other end of the side line in response to a pure traveling wave travel-.

ing through the main or first line in a direction corresponding to the direction from said oneend to said other end of the second line. The value of the effective resistance to be provided-by thee terminating resistors 64, 64 for this purpose is given by the relation:

R5 R .=R M 1 R1+R2 -k.=the coefficient of electric and magneticcouy- 1,,

This value of resistance is alternatively givenby l3 bling between the main and side lines and has the value: b r I k R1 R1+Ra In practice it is usually preferable-to terminate the other end of the side'transmission line by a similarresistive impedance comprising one or tors 65 and Bl may be connected -to respective ones of the resistors, 64, and 66 Where the trans: lating system is used as in the measuring system of Fig.3. The main and side transmission lines, have. electric and magnetic coupling over the.

length of the conductor 62 so that the length of this conductor should for maximum coupling,

be an odd number of quarter-wave lengths at a selected wave length of wavesignalstranslated through the translating system. The efficiency of the translating system is given by Equation 4 above if e of this equation is considered the length in radians of the conductor 62 .at the selected wave length.

While the resistors 64, 64 and 66, 66 are shown as coupled between the conductorsiiZ and 53, thus conveniently to permit conductors Biand 61 to .be connected to the resistors as when the translating system is utilized in a measuring systern of the Fig. 3 type; theside line may alternatively beselected as comprising the conductors E0, 52 in which case the terminating resistors 64, 64 and 56, 66 are connected between the hol low conductor 62 and the inner conductorfill.

This last-suggested connection of the resistors is V satisfactory for certain applications, but requires.

that the conductor Bil of the first line be hollow if circuit connections are to be completed to the;

resistors since the circuit conductors must then extend through the last-mentioned hollow con-V ductor. This alternative requires interchanging R1 and R2 in the Formulas 5 to 'Z The operation of the Fig. 5 translating system is essentially similar to that of the Fig. 1- are rangement except that much largerf values of thecoefiicient of coupling k between the main and side transmission lines may be'- ;readi ly at- I tained in the Fig.5 system. a consequence of this, the eliiciency of translation in the in stant arrangement may be made to vary over i a much wider range of values with the wavelength .values of translated wave signals so that the system may be readily designed to have a frequency-selective translation characteristic or a frequency-selective attenuation f characteristic.

This characteristic is gra'phically shown by the curv'e'o'f Fig. '6, wherein the translation efficiency is plotted 'against'thel length QfthesideIineSZ,

63 for a fixedgiven wave length remiered wave signals. It will be seen that substantial attenuation fortranslated wave signalsflis ef'-' wavelengths, long. Likewise, substantially no attenuation is provided for those wave signals having any 'wave length within a wavelength bandcentered upon the wave lengthat which. the conductor 62 is one 'half wave 'length, or an integral number of half-wave lengths, long.

characteristic of the translating system enables it to operate as a frequency-selective attenuator for wave signals traveling in either directionalong the main transmission line. The modified form ofwave-signal translating system illustrated in Fig. 7 is essentially sim-. ilar to that of Fig. 5, similar elements, being des-"Z ignated by similarv reference numerals and analogous elements by similar reference numerals primed. The size of the inner conductortfl' in a region 68 of length equal to that of the conductor 62 is the same as that of the conductor? 60 in Fig. 5, while the outer conductor. 61' has a uniform diameter the same as that of the conductor section 63 along its length. Here again; the conductor sizes. are selected to satisfy'Equa-.

tion' 5 tomaintain uniform characteristicimpedance along the main. transmission line. The operation and characteristics of this modified form of the invention areessentially similar to those of Fig. 5. i

Fig. ,8, with the cross-sectional viewof Fig. 8a, illustrates a wave-signal translating system essentially similar to that of Fig. 1 except that the of a rod 14 and has conductive contact fingers 15, as in the Fig. 1 arrangement, which conductively engage the inner walls of the housing. A sidetransmission line 16, 11 extends through the plate 73 into the housingll with the inner conductor of the side line parallel to the inner conductor 69 of the main line where these conductors arevexposed to one another withinthe housing. The side transmission line is terminated by a resistor 18 which corresponds to one of the resistors 2| or 22 of the Fig. 1 arrangement The width to of the housing is preferably much greater than its thickness t in order that the values of magnetic and electric coupling between the main and side transmission lines shall be determined mainly by the larger planar sides of width 10. The values of magnetic, and electric.

coupling then vary at the same rate with the displacement of the side line relative to the main.

line. The center conductor 69 of the mainline and the center conductor 16 of the side lineshould be centered between the sides of the hous-v ing in order that the undesired magnetic mode. of lower attenuation, which is determined by the width w of the housing, will not be excited or" picked'up. The exposed conductors of the main and side lines are preferably formed of'flat conductor strips to permit closer coupling with reasonable clearance between the conductors. It will be understood that the'cross-sectional size of the housing .H is selected to maintain the character istic impedance of the main and side transmissionlines uniform throughout their length in cluding the portions thereof which lie withinthe housing The Fig. 8 translating system is thus quite similar to that of Fig. 1 except that the inner conductors of the main and side transmission lines are exposed to one another over the entire v of the-inner conductor 'lfi of the-sidelineshould thus-have a lengthequal :to an odd number-pf quarter-wave :lengths'; Tha -operation of the FigE S tranS-Iating system-is essentially similar to that of Fig. 1 and-will not be repeated? An additionally modified form of theinventiom essentially: similarl-to thetranslatingsystempi. Figf fl but.:- suitable for use -with; 'an open pair- 4 or halancedttypeof transmission-line, is shownin Fig:2i9.. -'Ih'e.1main transmissionline is'of the 4 opentapairsrorbalanced type and-:includesa pair of parallel conductors sll Bit"; The side transmission .line: comprises' a pairlof hollo'w cylinders 82,1;83 op'enasat their ends and surrounding respectivennesrofzthe conductorsllfififi'l of the main:

line::.--;As in the arrangements 'of FigsI-LS- and l, the IlOIldllCtOlSlfiZi 83 have alengthi equal to an odd:numberzofsquarterswave: lengths ion-maxi mum'icouplingi'ands uniformityof coupling over a wavealength :hands Each :of: the sideeline Icondoctors-82 83 hastits axis :paralleliwith the-axis I g of a respective one of the conductors-480, flout displaced; thereiro-mitby a distancei such as to maintainaa. geometrici-meanrspacingh'etweenuthe v the;iother;-:;andaa:neutral*planamidway betweenti. the-:conductors-fifi;1:815 'i Thatris, theliconcluctors 80,18l-"0f the main. linezhaveiequi-potentialtsurs: faces surrounding :zthem :and the conductors .82. 1

83 of'the. sideline each'arer'located in individual though; ;,:equal and=opposite 'equipotential sure faces;-,-which: would existbetween thetconductors' Tomaintainiuniform characteristicimpedance along :the ,mainitransmissionlinexSfl, '3 l; the conductor 80 qhas0ver sthevlengthof -;the con.

ductor 8'2' a, section :84 of reduced :diameter and theconductor-Bl a similar-section 85 of reduced diametereoventheiengthof the conductor 83;:

The diameters -:of ,the' sections; 84' and 85 are :so

selected; bothlwithrelation to the diameters'ofi then-conductors -8 2:- and; i 83-: and the characteristic impedancejofithe. side :line; as to satisfy the fol- 1 wherein.

Lia

Ro'-"'- -the -characteristic impedance of the main line SIL- BI at a point spaced'from the'com ductorstZ, 83,111

Rz' tw-ice the characteristic impedance between the line-conductor section 84 and the' conductor: 82 or between-the line-conductor-- section-85 and theconductor 83, 'a11d- R1 'th\e" characteristic impedance 'ofthe side- The side. .transmissioniline 82, 83 islterminated" v at one'or .both ,endsby .a resistor 86 the value of which is. given by the relation: 7

If it is desired .to measure: the wave-signal powersupplied to either orboth of ,theresistors -a:

86, 8B, anammeter ll'lmay he'insertedinseries with the vresistoixat the mid-point. thereof" The operation of the Fig. 9 modified formiof theinvention is essentiallysimilar. to that .of Figl'do'r li'ig.- ll andiwillnot lee-repeated. V

Fig'lZilO. illustrates awave-signaltranslatingilf system embodying an additionally. modified .form r. l

of the; invention-Lessentially "similar: .to that of Fig. .19 fsimilar' elements. ,being. designated by similarl'ireference numerals and. .analogo us. elements by similar reference numerals primed, ex-

cept that the side transmission line iscomprised of a pair of parallel conductors 82, BS arranged as an open pair or'balanced transmission line with the conductors} thereof approximately equally spaced from"'corresponding conductors 80, 8L'of"-the -main"transmission line The air-- Figs-8 and wi1linotbe repeated;

It is the iunction of themaintransmission linef' in each of the fore'g'oin'g des'cribed "arrangements to guide or-efiect translation of Wave signals'along a propagation path and to ensure that such trans-' lated' wave" signalshavea substantially planar wave'tront'ralong the pathL-The wave frontof a wave-signal is identified bya' plane parallel -'to the perpendicular lines-of electrostatic and magneticiiux of thewave signal;- A wave signal hav'- ing 'a planar wave front inherently has electri field and-*magnetic fieldpatterns which vary only in two dimensions with the only variation in the third dimension being-one of time; the energy of the-wave signal being propagated in a certaindirection without appreciable changeof amplitude;

thatis, th'e'energyof the wave signal" must not be spreadingrioutward or focusing inward if the wavesignal-is to'ha'vea planar Wave front. =Such 11 twosdimensional field is' retained in the main and side lines' by making" theiransverse dimension of the "coupling aperture or slot muchless-" thanits longitudinal dimension. It will'be' ap parent-Ithat the side -line'82'; 83' 0f the Fig. 10 Y arrangement may itself-he utilized as a dire'c-' tional coupler for wave signalspropagated'-" through free space; the axes of the side-line con-" ductors in s'uchease pref erably being positioned normal to the'wav'e'front orthe propagated signal 1? for. maximum energy itransfer to the side line? When so utilized, the side line efie'ctively be-' comes a wave-signal antenna having a unidirec- 5 tional characteristicand may be utilized as such T Thesame' is true for the'coaxial typeof side line; such as that of Figs; 1, 2 or 3,101 example,-whe're the outer 'c'onducto'r 0f the sideline is provided with' a-slot or aperture, as the slot 20, by whichto effectdirection'arcoupling between'the side line'and' a'wave signal propagated through free" space;

From the-foregoing brief discussion of the directional'coupling with a, wave sign in f space, it will beseen that" the wave-signal trans-' latingsystem'pi thevinvention is one 'whichis adapted to 'be positioned 'along a path'of trans-'f lation fofpwave signals having a substantially planar'wave iront and comprisesawave-guide for translating Wave signals along a second path with substantially the same velocity as that of the; first path,the wave guide including at leasttwo" conductors having approximately parallel Sub stantially dissipationless conductor portions sepa-T rated" byz-a distance" muchles's than their length," and much less than the wave length of the trans I lated wave signals. These first and second paths Ti have magnetic-and electric coupling therebetween i only over limited approximately parallel portions. thereof. This'limiting of the coupling'is effected effected by shielding an inner conductor of the side line by an outer conductor thereof and by providing an elongated slot or aperture in such outerconductor by which to permit the magnetic fields of the translated Wave signal'to penetrate.

in a certain manner the interior of the shielded side line. The parallel portions of thepath last mentioned have such length in relation to the wave lengthof the wave Signals as to provide a desired amount of-coupling between the first and the second paths, a length of the parallel portions equal to an odd number of quarter wave lengths of the translated wavesignals providing maximum coupling as previously mentioned. The translating system of the invention includes means for terminating the wave guide at one end thereof by an impedance having such value that substantially no wave-signal energy is developed at the other end of the wave guide in response to a pure traveling wave traveling through the firstmentioned wave-signal propagation path in the region of the parallel portions of the pathsjand in a direction corresponding to the direction from the aforesaid one end to the aforesaid other end of the wave guide. 7 The energy transfer from the wave-signalpropagation path to the propagation path of the waveguide varies with the wave length and with the length of the parallel portions of thesepaths over which the magnetic and electric coupling is permitted even though the coefiicient of such coupling remains the same. The change of energy transfer with wave length varies more slowly, however, when the length of coupling between the two propagation paths is equal to an odd number of quarter-wave lengths at the mean wave length in the range.

For convenience of description of the invention, one of the transmission lines has heretofore been referred to as a side line and the other as a main line. Since the electric and magnetic coupling between the lines is effective, however, to transfer wave-signal energy from the main line to the side line or vice versa, it will be apparent that either transmission line may be the "main line and the other the side line.

It will be apparent from the foregoing description of the invention that a wave-signal translating system embodying the invention has the advantage that wave-signal energy is transferred from free space to a Wave guide or from'one wave guide to another with the direction and directional magnitude of wave-signalenergy flow in the second wave guide selectively dependent only upon an individual direction and directional magnitude of energy flow in free space or inthe system of the invention permits'a selected portion of the wave-signal energy traveling along a waveguide to be abstracted therefrom selectively in accordance with the direction of energy flow along such wave guide. Certain of the modified forms of the invention have the advantage forv certain applications that their translation chars acteristics may easily and readily be made that.

-18 of a band-passselector either to translate with little attenuation wave signals within a range of wave lengths or, conversely, to attenuate wave signals within .a range of wave lengths.

M While there have beendescribed what are .at

present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may bemadetherein without departing from the invention, and it is, there-- fore, aimed in the appendedplaimsto cover all such changes and modifications as fall --,within thetrue spirit and scopeof the invention; What is claimedis: I t i 1. A wave-signal translating systemadapted-to be-positioned along a path of translation of wave signals having-a substantially planar wave-front comprising, a wave guide having itslongitudin-al axis substantially parallel-tosaid path for tra'nslating wave signals along a second -path with substantially thesame velocity as that-of said first path and including a longitudinally extendingelongated aperture, said aperture having a length equal approximately to aquarter wave length at a selected wave length of said firstmentioned Wave signals, and-said wave-guide including at least two conductorshaving approximately parallel substantially dissipationless conductor portions separated bya distance-much less than their length -and-much lessthanthe wave length of said wave signals,- said paths adapted to have distributed magnetic andfelectric coupling therebetween throughsaid aper ture, and meansfor terminating said wave guide at one end thereof by an impedance having such value that substantially nowave-sig-nal energy is developed at the other end ofsaid wave guide in response to a pure traveling-wave traveling through said first-mentioned path in the region of said parallelportions and in a direc'tion corresponding to the direction from said one end to said other end of said Waveguide. I v

2. A wave-signaltranslatingsystem adapted-to be positioned along a-path of translation of wave signals having a substantially planar'wave front comprising, a coaxial transmission line having its longitudinal axis substantially parallel to said path for translating wave signals along-a second path with substantially the same velocity as that of said first path andincludingat le'ast twocoaxially supported conductors having ap proximately parallel substantially dissipationless conductor .portionsseparated "bya distance much less than their lengthand; much less than the wave length of said wave signals. theouter conductor of said'transmission-line having an elongated aperture having a length equal approximately to a quarter wave length at a selected wave length of said first-mentioned wavesignals for effecting magnetic and electric coupling between said paths only over limited approximately parallel portionsthereof and means for terminating said coaxial transmission line at one end thereof by an impedance having such value that substantially no wave-signal-energy is developed:

to be positioned-along a path of translationof Wave signals having asubstantiallyplanar wave;

front comprising, a coaxial transmission line having its longitudinal axis substantially parallel to saidpath for translating wave signals along a second path with substantially the same vesipationless conductor portions separated by a distance much less than their length and much less than the wave length of said wave signals, the outer conductor of said transmission line having a longitudinally extending elongated aperture having a length equal approximately to a quarter wave length at a selected wave length of said first-mentioned wave signals for efi'ecting magnetic and electrical coupling between said paths over a longitudinal length thereof equal approximately to an odd number of quarter- 'wave lengths at a selected wave length of wave 'wave signals having a substantially planar wave front comprising, a coaxial transmission line having its longitudinal axis substantially panallel to said path for translating wave signals along a second path with substantially the same velocity as that of said first path and including at least two coaxially supported conductors having approximately parallel substantialy dissipationless conductor portions separated by a distance much less than their length and much less than the wave length of said wave signals, the outer conductor of said transmission line having a longitudinally extending elongated aperture having a length equal approximately to a quarter wave length at a selected wave length of said first-mentioned wave signals for efiecting magnetic and electric coupling between said paths over a longitudinal length thereof equal approximately to a quarter-wave length at a selected wave length of wave signals translated through said first-mentioned path, and means for terminating said coaxial transmission line at one end thereof by an impedance having such value that substantially no wave-signal energy is developed at the other end of said coaxial transmission line in response to a pure traveling wave traveling through said first-mentioned path in the region of said parallel portions and in a direction corresponding to the direction from said one end to said other end of saidcoaxial transmission line.

5. A wave-signal translating system comprising, a first coaxial transmission line for effecting the translation of wave signals along a first predetermined path and with a substantially planar wave front, a second coaxial transmission line for translating wave signals along a second predetermined path with substantially the same velocity as that of said first path, said lines each including at least two conductors having approximately parallel substantially dissipationless conductor portions separated by a distance much less than their length and much less than the wave length of said wave signals and said lines having therebetween at the region of said conductor portions a common intercommum'cating longitudinal aperture having a length equal approximately to a quarter wave length at a selected wave length of said first-mentioned wave signals for efiecting magnetic and electriccoupli'ng between said lines only over approximately parallel portions thereof, and means for terminating said second transmission line at one end thereof by an impedance having such value that substantially no wave-signal energy is developed at the other end of said second transmission line in response to a pure traveling wave traveling through said first transmission line in the region of said parallel portions and in a direction corresponding to the direction from said one end to said other end of said second transmission line.

6. A Wave-signal translating system comprising, a first coaxial transmission line for effecting the translation of Wave signals along a first predetermined path and with a substantially planar wave front, a second coaxial transmission line positioned in coaxial relation to said first line with a conductor common to both of said lines for translating wave signals along a second predetermined path with substantially the same velocity as that of said first path and including at least two approximately parallel substantially dissipationless conductor portions separated by a distance much less than their length and much less than the wave length of said wave signals, said common conductor having an elongated aperture having a length equal approximately to a quarter wave length at a selected wave length of said first-mentioned wave signals for efi'ecting magnetic and electric coupling between said lines only over approximately parallel portions thereof, and means for terminating said second transmission line at one end thereof by an impedance having such value that substantially no wave-signal energy is developed at the other end of said second transmission line in response to a pure traveling wave traveling through said first transmission line in the region of said parallel portions and in a direction corresponding to the direction from said one end to said other end of said second transmission line.

7. A wave-signal translating system comprising, a first coaxial transmission line for effecting the translation of wave signals along a first predetermined -path and with a substantially planar wave front, a second coaxial transmission line having an outer conductor spaced in concentric relation to the outer conductor of said first line to utilize said last-rl'lentionedconductor as the inner conductor of said second line and to eiTect translation of Wave signals along a second path with substantially the same velocity as that of said first path, said lines each including at least two approximately parallel substantially dissipationless conductor portions separated by a distance much less than their length and much less than the wave length of said wave signals, and said last-mentioned conductor having an elongated aperture having a length equal approximately to a quarter wave length at a selected wave length of said first-mentioned wave signals for effecting magnetic and electric coupling between said lines only over approximately'parallel portions thereof, and means for terminating said second transmission lineat one end thereof by an impedance having such value that substantially no wave-signal energy is developed at the 21 other end of said second transmission line in response to a pure traveling wave traveling through said first transmission line in the region of said parallel portions and in a direction corresponding to the direction from said one end to said other end of said second transmission line.

8. A wave-signal translating system comprising, a first transmission line having inner and outer conductors coaxially arranged and adapted to translate wave signals along a predetermined path between said conductors, a second transmission line having a length equal approximately to an odd number of quarter wave lengths at a selected wave length of wave signals translated along said path, said second transmission line also comprising a hollow conductor open at both ends and coaxially surrounding the inner conductor of said first line but spaced from both conductors thereof, said transmission lines having magnetic and electric coupling therebetween only over limited approximately parallel portions thereof, and means for terminating said second transmission line at one end thereof by an impedance having such value that substantially no wave-signal energy is developed at the other end of said second transmission line in response to a pure traveling wave traveling through said first transmission line at the region of said parallel portions and in a direction corresponding to the direction from said one end to said other end of said second transmission line.

9. A wave-signal translating system comprising, a first transmission line having inner and outer conductors coaxially arranged and adapted to translate wave signals along a predetermined path between said conductors, a second transmission line having a length equal approximately to an odd number of quarter wave lengths at a selected wave length of wave signals translated along said path, said second transmission line also comprising a hollow conductor open at both ends and coaxially surrounding the inner conductor of said first line but spaced from both conductors thereof, said transmission lines having conductor sizes so selected over the length of said second line as to provide a combined impedance for said lines substantially equal to the characteristic impedance of said first line at a point therealong spaced from said second line and to establish between said lines a desired amount of magnetic and electric coupling, and means for terminating said second transmission line at one end thereof by an impedance having such value that substantially no wave-signal energy is developed at the other end of said second transmission line in response to a pure traveling wave traveling through said first transmission line in a direction corresponding to the direction from said one end to said other end of said second transmission line.

10. A wave-signal translating system comprising, a first transmission line having inner and outer conductors coaxially arranged and adapted to translate wave signals along a predetermined path between said conductors, a second transmission line having a length equal approximately to an odd number of quarter wave lengths at a selected wave length of wave signals translated along said path, said second transmission line also comprising a hollow conductor open at both ends and coaxially surrounding the inner conductor of said first line but spaced from both conductors thereof, said transmission lines having conductor sizes so selected over the length of said second line as to provide a combined impedance for said lines substantially equal to the characteristic impedance of said first line at a point therealong spaced from said second line and to establish between said lines a desired amount of magnetic and electric coupling, and resistive means coupled between said hollow conductor of said second line at one end thereof and one conductor of said first line for terminating said second line by a resistive impedance having such value that substantially no wavesignal energy is developed at the other end of said second line in response to a pure traveling Wave traveling through said first line in a direction corresponding to the direction from said one end to said other end of said second line.

11. A wave-signal translating system comprising, a first transmission line having inner and outer conductors coaxially arranged and adapted to translate wave signals along a predetermined path between said conductors, a second transmission line having a length equal approximately to an odd number of quarter wave lengths at a selected wave length of wave signals translated along said path, said second transmission line also comprising a hollow conductor open at both ends and coaxially surrounding the inner conductor of said first line but spaced from both conductors thereof, said transmission lines having magnetic and electric coupling therebetween only over a length thereof approximately equal to said odd number of quarter-wave lengths to provide maximum coupling from said first line to said second line for any given conductor sizes for said lines, and means for terminating said second transmission line at one end thereof by an impedance having such value that substantially no wave-signal energy is developed at the other end of said second transmission line in response to a pure traveling wave traveling through said first transmission line in a direction corresponding to the direction from said one end to said other end of said second transmission line.

HAROLD A. WHEELER.

REFERENCES CITED The following references are of record in the file of this patent:

. UNITED STATES PATENTS Number Name Date 2,239,905 Trevor Apr. 29, 1941 2,423,390 Korman July 1, 1947 2,423,416 Sontheimer et a1. July 1, 1947 2,423,526 Sontheimer July 8, 1947 2,478,317 Purcell Aug. 9, 1949 2,519,734 Beth Aug. 22, 1950 2,562,281 Mumford July 31, 1951 OTHER REFERENCES en's 

